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Date: Tue, 29 Dec 2020 16:00:59 +0000 From: David Brazdil <dbrazdil@...gle.com> To: kvmarm@...ts.cs.columbia.edu Cc: Marc Zyngier <maz@...nel.org>, James Morse <james.morse@....com>, Julien Thierry <julien.thierry.kdev@...il.com>, Suzuki K Poulose <suzuki.poulose@....com>, Catalin Marinas <catalin.marinas@....com>, Will Deacon <will@...nel.org>, Mark Rutland <mark.rutland@....com>, Lorenzo Pieralisi <lorenzo.pieralisi@....com>, Sudeep Holla <sudeep.holla@....com>, linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org, kernel-team@...roid.com, David Brazdil <dbrazdil@...gle.com> Subject: [PATCH] KVM: arm64: Allow PSCI SYSTEM_OFF/RESET to return The KVM/arm64 PSCI relay assumes that SYSTEM_OFF and SYSTEM_RESET should not return, as dictated by the PSCI spec. However, there is firmware out there which breaks this assumption, leading to a hyp panic. Make KVM more robust to broken firmware by allowing these to return. Signed-off-by: David Brazdil <dbrazdil@...gle.com> --- arch/arm64/kvm/hyp/nvhe/psci-relay.c | 13 +++++-------- 1 file changed, 5 insertions(+), 8 deletions(-) diff --git a/arch/arm64/kvm/hyp/nvhe/psci-relay.c b/arch/arm64/kvm/hyp/nvhe/psci-relay.c index e3947846ffcb..8e7128cb7667 100644 --- a/arch/arm64/kvm/hyp/nvhe/psci-relay.c +++ b/arch/arm64/kvm/hyp/nvhe/psci-relay.c @@ -77,12 +77,6 @@ static unsigned long psci_forward(struct kvm_cpu_context *host_ctxt) cpu_reg(host_ctxt, 2), cpu_reg(host_ctxt, 3)); } -static __noreturn unsigned long psci_forward_noreturn(struct kvm_cpu_context *host_ctxt) -{ - psci_forward(host_ctxt); - hyp_panic(); /* unreachable */ -} - static unsigned int find_cpu_id(u64 mpidr) { unsigned int i; @@ -251,10 +245,13 @@ static unsigned long psci_0_2_handler(u64 func_id, struct kvm_cpu_context *host_ case PSCI_0_2_FN_MIGRATE_INFO_TYPE: case PSCI_0_2_FN64_MIGRATE_INFO_UP_CPU: return psci_forward(host_ctxt); + /* + * SYSTEM_OFF/RESET should not return according to the spec. + * Allow it so as to stay robust to broken firmware. + */ case PSCI_0_2_FN_SYSTEM_OFF: case PSCI_0_2_FN_SYSTEM_RESET: - psci_forward_noreturn(host_ctxt); - unreachable(); + return psci_forward(host_ctxt); case PSCI_0_2_FN64_CPU_SUSPEND: return psci_cpu_suspend(func_id, host_ctxt); case PSCI_0_2_FN64_CPU_ON: -- 2.29.2.729.g45daf8777d-goog
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